Portable radiotelephones are increasingly utilized to permit a user to communicate telephonically over a wireless system at virtually any location. The portable telephone transmits a low wattage, radio frequency signal to a receiving station, which may be connected with conventional landline telephone systems.
Portable radiotelephones having two housings joined by a type of hinge that allows the housings to fold upon one another are known in the art. Some such folding radiotelephones have most of the electronics in one housing called the main housing and fewer electronics in the other housing, called the cover. Other such folding radiotelephones have all the electronics in the body with the cover serving only to cover the keypad or keypad and display of the phone.
Some known portable cellular radiotelephones utilize, as shown in FIG. 6, a hinge mechanism having a spring 642 and hinge pins 636, 648 disposed in a tubular hinge arm 624 formed at an end of a cover 606, and bushings 660 formed in body 612. Spring 642 is positioned between hinge pins 636, 648, and at all times outwardly forces hinge pins 636, 648 from cover 606 to body 612. Examples of such known radiotelephones are described in PCT Publication No. WP 93/18592, published Sep. 16, 1993 and U.S. Pat. No. 5,274,882, issued Jan. 4, 1994.
Although suitable for some foldable radiotelephones, such a hinge mechanism as described above is not suitable for miniaturized foldable radiotelephones. The housings of the miniaturized radiotelephones do not have sufficient bulk and material strength to bear the spring's outwardly directed compressive forces. Also, the smaller housing makes it more difficult to assemble the hinge elements.
U.S. Pat. No. 5,628,089 by Wilcox et al., entitled "Radiotelephone Having a Self Contained Hinge," issued May 13, 1997, and assigned to Motorola, Inc. discloses a hinge for use in a miniaturized radiotelephone. The hinge 301 comprises a spring 405, a cam 404 and a follower 403 assembled into a cylindrically hollow can 303 via an open end thereof and held in assemblage by a cap 305 coupled to the can 303 over the open end. The assembled hinge 301 in can 303 is disposed in a cavity 307 of cover 103 and a cavity 503 of body 101. The self contained hinge may be desirable to some radiotelephone manufacturers because it can be purchased as a separate unit, thereby eliminating the steps associated with assembling the hinge during manufacturing. However, because the hinge includes a can to hold the hinge components together, the number of parts used and the cost of the hinge is increased.
Thus, a need exists for a self contained hinge for use in a miniaturized foldable device, such as a portable radiotelephone, that minimizes the number of parts and cost of the hinge.